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Re: Abs[a] Sin[Abs[a]]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg21025] Re: [mg20923] Abs[a] Sin[Abs[a]]
  • From: BobHanlon at aol.com
  • Date: Thu, 2 Dec 1999 21:41:36 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Edward,

Since both

Simplify[Abs[a]*Sin[Abs[a]], a >= 0]

a Sin[a]

and

FullSimplify[Abs[a]*Sin[Abs[a]], a < 0]

a Sin[a]

then

Abs[a]*Sin[Abs[a]] /. Abs[x_]*Sin[Abs[x_]] :> x*Sin[x]

a Sin[a]

Or, since

FullSimplify[Abs[a] == a*Sign[a], Element[a, Reals]]

True

then

FullSimplify[Abs[a]*Sin[Abs[a]] /. Abs[x_] :> x*Sign[x], Element[a, Reals]]

a Sin[a]


Bob Hanlon

In a message dated 12/1/1999 3:19:20 AM, gold at isitel1.isi.kfa-juelich.de 
writes:

>How to compell Mathematica to simplify
>  Abs[a] Sin[Abs[a]]
>to
>  a Sin[a]
>
>?
>Why it does not do it automatically? I also tried 
>assumptions like a :enum: Reals.
>


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